Bacterial and Processing Modifications for Efficient Ethanol Production from Biomass

Bacterial Modifications and Processing Treatments Allow for Efficient Conversion of Sugars into Ethanol

These biomass-processing methods and bacterial biocatalysts enable more efficient and cost-effective ethanol production from lignocellulosic biomass. Lignocellulose is composed of lignin, cellulose and hemicellulose; the latter two components are sugar polymers that when broken down sufficiently can provide the carbohydrate source for fermentation into products such as ethanol. Unlike cornstarch, which is currently the leading source of carbohydrate for biofuel production, the structure of lignocellulose makes it more challenging to be broken down into its component sugars, making chemical and enzymatic pretreatment essential for conversion into ethanol. Acid pre-treatment makes cellulose more accessible for further enzymatic digestion as well as hydrolyzes some of the hemicellulose. However, this acid pre-treatment creates an unwanted byproduct called furfural that inhibits fermentation by the bacterial biocatalysts, thus decreasing production efficiency. Researchers at the University of Florida have developed bacterial modifications and processing methods that overcome this inhibition and allow for efficient conversion of sugars into ethanol.

Application

Production of ethanol biofuel from lignocellulosic biomass

Advantage

• Makes lignocellulose biomass conversion more efficient, potentially lowering production time, costs, and adoption barriers

Technology

University of Florida researchers have developed a series of processing treatments and bacterial (biocatalyst) modifications that increase the efficiency of ethanol production from lignocellulosic biomass. Lignocellulose is composed of carbohydrate polymers (cellulose and hemicellulose) containing both hexose (six-carbon) and pentose (five-carbon) sugars as well as lignin. Most ethanol biorefineries use yeast biocatalysts to ferment the sugars into ethanol, but yeast is only able to utilize hexoses. The bacterial biocatalysts developed at the University of Florida can utilize both hexose and pentose sugars and thus produce more ethanol from the same weight of biomass than with yeast biocatalysts. The most cost-effective pre-treatment of lignocellulosic biomass requires the use of strong acids, but this also leads to the production of a small amount of furfurals, due to pentose dehydration, which inhibit fermentation. Dr. Ingram’s team has identified a number of process steps that minimize furfural production and have made a series of genetic modifications to the bacteria to minimize furfural inhibition.